For the sentences provided:

**Câu 10**: The best choice is **C: much more relaxing**. So the complete sentence would be: "I think you'll find going fishing much more relaxing than playing mobile games."

**Câu 11**: The correct option is **B: less convenient than**. The complete sentence would be: "Doing shopping in the countryside is less convenient than that in cities."

Let me know if you need further assistance!